The service quality survey for the customers of Gwangyang container port has been done since 2005. It has been difficult to compare annual levels or rival ports because the calculation of weights among service dimensions that is the most important procedure of the assessment systems did not be founded. In particular, the calculation results by the Analytical Hierarchy Process that specializes in estimating the weights were very unstable and not comparable because they were fluctuated annually more than 90% for the specific item. The objective of this study is to support the establishment for new assessment system of service quality with cost- and time-effective tools at Gwangyang port. The confirmatory factor analysis methodology applied to 2007-2009 survey data from the customers of Gwangyang port can estimate ex-post weights to measure annually the stable service quality. The proposed methodology allows us to build the assessment system of more scientific and accurate service quality while reducing the survey items. By this study, a port company can measure accurately the quality of service and improve its competitiveness through being compared to previous periods and leading companies.